Ultra high frequency coupler between contiguous ends of aligned wave guide sections



`lune 21, 1949. E. c. oKREss ETAL 2,473,724

ULTRA HIGH FREQUENCY COUPLER BETWEEN CONTIGUOUS ENDS OF ALIGNED WAVE GUIDE SECTIONS Filed sept. 24, 1945 INVENTORS E. C. @MEE-55 f7. H, Amp/G BW www ATTORNEY Patented June 21, 1949 UNITED STAT-ss raNr oFFICE ULTRA. HIGH-FREQUENCY" COUPLER BE- TWEEN `CONTIGUOUS ENDS 0F ALIGNEli)l WAVE-GUIDE SECTIONS,

Application September 24, 1943, Serial No. 503,628

4 Claims..

This invention relates-to cavity joints and more particularly to joi'nt'sbetweenv hollow instrumentalitiessuch kas sections vof wave guides and 'a generator the outlet of' which-isof hollow character.

The usent-Wave guidesiforpurpose of Atransfer oradio or'ultra high'irequency energy from place toplace is lan accomplished' fact; Itis, however, important' that there'becontinuity for the mode ofA propagation along the--wave guide from the generator to theins'trument' to which the energy is being conveyed.y Screw threaded joints are generally inefficient when usedin linesv conveying R. F." currents. Priorpractice` has been tof obtain surface continuity bysoldering or otherwise definitely sealingy all joints. ThatV procedure is satisfactory for'xthe electrical conductivityvv requirements, but has itsdeciencies from practical considerations; Principal Vamong theV shortcomings of the' prior art is the difliculty in making changes, additions and substitutions-inthe assembly. Anotherv adverse con-dition' encountered in" the prior artis the frequentpsituations encountered making' accessto joints fory obtaining` a good soldering thereof. extremely diiiicult. A wave guide generally is air filled'I whereas 'the'generatoris evacuated and prior `practice hasbeen to provide some form of concentric line` through'a seal from the evacuated generator to theenon-eva'cuated wave guide. This has presentedbothy mechanical and electrical'difiiculties.. In its most general aspects, A

therefore, the invention. seeks 'to' overcome the deficiencies, drawbacks ar'iddiitlc'zultiesv of the prior art..

More speciically,"an object ofthe invention is to improve upon the'prior'art arrangements effecting the'. mechanical and electrical coupling of a generator or other evacuated instrumentalit i7 to a Wave guide.

Another-object of the .invention is to provide a mechanical couplingl and joint which 'also vacuum seals the generator..

A furtherv object of the invention is to provide such'a mechanical coupling'which permits use of a threaded` connection as' the. releasable means for interchange of' generator or'other, purposes.

Yet another object ofthe invention4 is to provide. a construction which functions as a .me-

. chanical andfelectricalv coupling from. generator to wave guide andas a vacuum seal for the generator.

, Still vfurther objects "ofthe invention will appear as):the'.description'` prOgfe'sses, both by direct referenceYV thereto and by implication from the context.

Referring: to'.l the-accoinpanying drawing' in Vwhich like numerals of reference indicatev similar parts throughout the severalviews;

Figure 1 is a sectional view, as on line I-I of Fig.` 2 of'a generatorl and wave guide showing the invention therewith;`

Figure 2 is a sectional view taken on line II-II of Fig'. 1;

Figure 3 is a sectional view of they coupling member forming part of the generator and'showing a protection shield applied thereon for shipping or storage purposes;

Figure 4 is a sectional view similar to Fig. 1 and' showing a modiiied construction ofl coupling members; and

Figure 5 is a sectional .Viewl similarv to Fig. 2 and showing a modi'ed. configuration of impedance matchingA slot.

In. the specific embodiment of theA invention illustrated in said drawing, and describing the structure of Figs. 1 and 2 initially, the reference numeral!!! designates generally .an ultra high frequency` wave.generator,. and which,.inthis par'- ticular showing is a magnetron. Such a generator includes a more or less hollow interior under vacuum and in which is situated a cathode II' parallel to a generally cylindrical anode li2'wherein are provided a seriesofcavities I3 opening toward the cathode and also opening into end spaces I4 in the magnetron. An output extends from one oi?k these end spaces I4, and'is, as shown, usually a coaxial line consisting offa tubular 'outer member I5 and a coaxial rod or innerv member I6 longitudinally therein and coextensive therewith. 'Ihe end of the inner member I6 is shown extending into end space I4 and bent laterally for support in. an appropriate socket in` the anode; whereas the outer end of said inner member is carried at the middle of a cap. I1 closing the outer endof the` outer member.- Heretofore it has been general practice to provide a ceramic seal, such as a glass bead, in the outer member as near the magnetron aspracticable,V the bead sealing onto the inner member as well as the outer member, theresult of which has been to have one end por-J tion of the output under vacuum and the other end under atmospheric pressure. Inclusion of, such abead has. not only represented mechanical difficulties but also a loss. ofv efficiency due to absorption of theY energy developed in the magnetron. According to the present invention, the entire interior of the outer member I5 is consti--Y tilted' a continuous cavity and; is under vacuumand. includes no insulative bead' whatever. End cap. I1 is of metal and is located a distance Li fromth'e center of theguide corresponding tol a definite series reactance in conjunction with the cap 28 at distance Lz providing the requisite radiation resistance for whatever operating point is chosen for the magnetron.

Extending laterally from the coaxial line output is a wave-guide section I8 of rectangular cross-section that it may be responsive to and selective of desired mode of wave propagation. The dimensions of both the coaxial line output and the wave guide have definite relation to the wave length compatible to the generator and of wave length desired for propagation in the wave guide.

The outer member I of the coaxial line and the wave guide section are sealed, as by solder I 9 at the joint therebetween.. One end of the wave guide section is also sealed with a plug 20. At the other end of the wave-guide section is another wave guide section 2l alined with the first section which is sealed thereat and which provides means for mechanically and electrically coupling the sections. This means constitutes an essential feature of the present invention. A primary consideration is to seal the rst wave-guide section vacuum tight and permit application of a second section, which is open to atmospheric pressure, such that the coupling and uncoupling of the joint does not affect or destroy the vacuum retaining characteristic of the rst section.

Exemplary of means accomplishing the desideratum just set forth, the substantially abutting .ends of the wave-guide sections I8, 2l or other instrumentalities are mechanically coupled with a clamping ring 24 securing those members together. More in detail, one said member 22 on the section Il?. of wave guide carried by the coaxial line and magnetron, provides a sleeve-like body portion 25 snugly fitting upon the marginal end of said member so the outer or front ends of said body portion and Wave-guide section are substanof member and wave-guide end. The forward face of the rim is likewise well rearward from said plane.

Vacuum-tight sealing of the wave-guide section I8 is obtained by a seal with respect to the forward face of said member 22. As shown, the forward face of rim 21 of said member 22 is provided with a circular groove in which the rear margin of a cylindrical metallic collar 29 is seated and sealed, as by solder 36. The forward edge ofsaid collar extends substantially to the aforesaid plane of the forward flush ends of member and Waveguide. A glass or other dielectric or capping means such as disc 3| situated substantially in said plane across the end of the wave-guide, has its rim sealed on the forward margin of said collar 29. By preference said collar is an alloy primarily of iron, nickel, cobalt and manganese described in Patent 2,062,335 of Dec. 1, 1936, and the glass is preferably a boro-silicate glass having an expansivity of 3.0 to 6.5 6 centimeters per centimeter per degree centigrade to substantially equal the expansivity of the alloy. The construction shown enables the glass capping to be in actual. contact with the forward face of the member 22.

Complementary member 24 of the coupling is LEO shown with a sleeve-like body portion 32 snugly fitting upon the rear marginal end of the waveguide section 2I so that its rear face and the rear end of the section are substantially flush that is, are in a common plane, and may be brought into close proximity to or contact with the forward face of the capping disc 3 I. These parts are securely soldered, as at 33. While the opening through the body portion 32 of said complementary member 24 is rectangular for obtaining the tting engagement and support of the member upon the Wave-guide section 2I, the permetric rim of said member is formed as a cylindrical rearwardly directed ange 34 large enough to pass the edge of the capping disc 3! and have its rear edge seat against the forward face of the rim 21 of the first-described primary member 22. This construction obtains exact spacing of the respective body portions of said members and prevents pressure being applied against the glass of the capping disc when said members are clamped together. By appropriately shouldering the forward face of the rim 21 of the primary member to receive the end edge of the iange .'54 of the complementary member, the members will precisely centered, and may be oriented angular-ly of the axis by a suitable lug 35 (shown in dotted lines in Fig. 1) projecting from the edge of the flange 34 into a corresponding socket in the rim 21.

ASaid members are clamped together when desired to assemble a second section 2l of wave guide to the magnetron-mounted section Iii, by clamping ring 24 the peripheral wall of which overlies the ange 34 of the complementary member and the inner edge margin of which is screw threaded to engage with threads 22 on the pcriphery of the rim 21 of the primary member. An inwardly directed wall 36 of this clamping ring engages on the forward face of complementary member and presses that member against its seat on the rim 21. Unscrewing of this clamping ring releases said members, but in no wise disturbs the vacuum seal of the capping disc or the magnetron-mounted section. A suitable protection shield 31 may be provided to be applied to threads 28 and overlie the capping disc when the magnetron is shipped or left unattached from a second wave-guide section.

Each body portion 25, 32 of said members 22, 23, has a slot 38 therein which opens toward the capping disc, said slots being directly opposed to each other and each completely engirdling its respective wave-guide section. As shown in Fig. 2, said slots preferably parallel the waveguide wall nearest thereto, so in end view said slot is shown as a rectangle. However, said slots may be circular,4 and exemplary thereof a circular slot 38 is shown in Fig. 5. Otherwise the structure of Fig. 5 is the same as heretofore described with respect to Figs. 1 to 3. In any event, the slot has a depth parallel to the wave guide which is equal to substantially a quarter-wave length of the waves in air or vacuum. Furthermore, the slot is preferably at approximately a distance outward from the wave-guide equivalent to a quarter wave-length of the wave in the glass or other medium comprising capping disc 3l and which, in the case of a glass disc, results in a much shorter wave-length therein than in air or vacuum. Accordingly, from wave guide to the bottom of said slot, represents a path of half a wave length. As a result, a very low impedance appears at the gap between the ends of the wave-guide sections, and

as a result those ends presentl the equivalent of electrical continuity for practically unimpaired transf'erfof the radio frequencyffrom the rst section |18 tofthe. second section. ;2 l5

Fundamentally.theconstruction of Figure 4 is thesameas .that heretofore; described, the diierw encesibeing of amechanicalcharacter for. aifordingia: measure. of protection tu? the capping disc when:thecoupilingmembers.are disconnected; As shown im Fig. .4, accordingly wav-eiguide sections IRI andi. 2 I fare arranged as. befo-rer. each-.having a coupling member 22' and 23 secured thereon and provided with a slot 38 therein of quarter wavelength depth. Rim 21 of the primary member 22 receives and retains a cylindrical metallic collar 29, preferably of the aforementioned alloy to which is sealed capping disc 3|, preferably of boro-silicate glass. This disc, as before, is preferably in the plane of and contact with the forward face of the primary member and end of the first wave-guide section, and substantially lls the gap between the two members and wave-guide secltions in the region between the wave guides and slots as before.

The diiference in construction of the showing of Fig. 4 over the previously described construction is to be found in provision of a, separately formed peripheral housing 39 of cylindrical configuration and appropriate size to be applied around the periphery of rim 21 and soldered or otherwise secured thereto. This housing extends forwardly to also overlie the edge of the capping disc, out of contact therefrom, and shoulders inward, at 40 and then forwardly at 4I with a smaller diameter so as to be permanently in front of the margin of the capping disc and thereby protect said disc. The forward projection 4I is externally screw threaded at 28' and receives clamping ring 24', an inwardly directed wall 36' of which overlies the complementary member 23 and holds it in place as will be understood from description of Figures 1 and 2. Lug and socket, slot and key, or other orienting means are also provided.

The embodiments of the invention selected for present illustration accordingly provide a permanent seal for the end of a wave-guide section -L which opens into a coaxial line from a magnetron or other generator enabling said generator, coaxial line and wave-guide section to all ybe evacuated as a single operation. Furthermore the construction eleminates obstruction to energy transfer in the coaxial line and aifords a single eiective means for transfer from the wave-guide section to a contiguous section with said means having the added function of mechanically coupling said sections.

We claim:

1. A cavity joint comprising contiguous wave guide sections each having its walls aligned with the walls of the other section, a coupling member on each said section on the contiguous ends thereof, and a dielectric capping means between said members and sealed with respect to one of the same and extending across the contiguous ends of both of the wave guide sections, one of said members providing a slot opening toward the said dielectric capping means a distance from the wall of the wave guide section substantially equal to a quarter wave length in the dielectric.

2. A cavity joint comprising contiguous wave guidev sections each having its walls aligned with the walls of the other section, a coupling member on each said section on the contiguous ends thereof, and a dielectric capping means between said members and sealed with respect to one of the same and extending across the contiguous ends of bonifici-fthe wave: guideasections, one of said members providing a slot ,opening toward the said dielectric capping; meansv a...distance;;from the. walllothe Wave*y guidepsection substantially equalt'o a quarter vwave,length in; the dielectric, said slot",v having a quarterwave: length; depth, whereby awlow4 impedance is. reflected-through slot. and?dielectricv togtheigap' betweensections occupied. .by said" dielectric.' fori obtaining' .effective electricalcontinuity'to radio 'frequency across the gap from one section to the other.

3. A lcavity joint comprising wave guide sections positioned endwise one to the other thereby providing contiguous ends, each section having walls in common planes with walls of the other section, and providing a gap between contiguous end of said sections, a coupling member on the exterior of each of said sections next the contiguous ends thereof and providing a continuation of said gap Ilaterally outward from said sections, each said member havingv a wave-guide opening therethrough, a dielectric'capping means in said gap sealing one said opening of one said member and extending laterally outward beyond said wave guide and between said coupling members, said capping means having a peripheral rim entirely outside of and remote from said wave guide and sealed with respect to said one member, and one of said members having a slot exterior to and completely girdling the wave guide in parallelism thereto and at a distance therefrom substantially equal to a quarter wave length in the dielectric and intersecting said dielectric between the rim of the dielectric and the wave guide.

4. A cavity joint comprising wave guide sections positioned endwise one to the other thereby providing contiguous ends, each section having walls in common planes with walls of the other section, and providing a gap between contiguous ends of said sections, a coupling member on the exterior of each of said sections next the contiguous ends thereof and providing a continuation of said gap laterally outward from said sections, each said member having a wave-guide opening therethrough, a dielectric capping means in said gap sealing one said opening of one said member and extending laterally outward beyond said wave guide and between said coupling members, said capping means having a peripheral rim entirely outside of and remote from said wave guide and sealed with respect to said one member, and one of said members having a slot of depth substantially equal to a quarter wave length in air, said slot being exterior to and completely girdling the wave guide in parallelism thereto and at a distance therefrom substantially equal to a quarter wave length in the dielectric and intersecting said dielectric between the rim of the dielectric and the wave guide.

ERNEST C. OKRESS. ALFRED H. LAIDIG.

REFERENCES CITED The following referenrces are of record in the le of this patent:

UNITED STATES PATENTS (Other references on following page) UNITED STATES PATENTS Number Name Date Zimmerer et al. Apr. 6, 1937 Dittmeyer May 24, 1938 Southworth Sept. 13, 1938 Van Mierlo Nov. 26, 1940 Newhouse Nov. 26, 1940 Lempert et al. -1 Apr. 14, 1942 Clifford Feb. 16, 1943 Number 8 Name Date Litton Mar. 2, 1943 Percival Oct. 12, 1943 Atlee et al Feb. 1, 1944 Varian et al Apr. 4, 1944 Allerding June 20, 1944 Ludi Dec. 12, 1944 Fiske Sept. 3, 1946 Mieher Sept. 10, 1946 

